4.6 Power Supply
There are two ways to provide power to the kit:
• The kit can be connected to, and powered by, a Silicon Labs MCU STK
• The kit can be connected to, and powered by, a Raspberry Pi
Note:
Connecting the WFM200S Wi-Fi Expansion Kit to both an EFM32/EFR32 STK and a Raspberry Pi at the same time is not a valid
option.
When connected to a Silicon Labs MCU STK, the WFM200S Wi-Fi Transceiver Module can either be powered by the VMCU rail
present on the EXP header or through an LDO regulator on board the WFM200S Wi-Fi Expansion Kit. If connected to the VMCU rail of
the starter kit, the current consumption of the WFM200S Wi-Fi Transceiver Module will be included in the starter kit's on-board Ad-
vanced Energy Monitor (AEM) measurements. The LDO regulator draws power from the 5V net, and, hence, the power consumption of
the WFM200S Wi-Fi Transceiver Module will not be included in any AEM measurements performed by the MCU STK.
A mechanical power switch on the WFM200S Wi-Fi Expansion Kit is used to select between Low Power (AEM) mode and High Power
(LDO) mode. When the switch is set to Low Power (AEM) mode, the WFM200S Wi-Fi Transceiver Module is connected to the VMCU
net on the Expansion Header. When the switch is set to High Power (LDO) mode, the WFM200S Wi-Fi Transceiver Module is connec-
ted to the output of the LDO. For applications requiring high power consumption or when the WFM200S Wi-Fi Expansion Kit is connec-
ted to a Raspberry Pi, the power switch must be set to High Power (LDO) mode.
A 0.1 ohm current sense resistor accompanied by a 2x2-pin 0.1" unpopulated header is provided to measure the current consumption
of the WFM200S Wi-Fi Transceiver Module whenever AEM is not available or when the current consumption exceeds the measure-
ment range of AEM.
The power topology is illustrated in the figure below.
Expansion
Header
Raspberry Pi
Connector
Power
Switch
Low
Power
(AEM)
High
Power
(LDO)
VMCU_NCP
LDO
IN
OUT
3.3 V
5V
3V3
WFM200S
0.1Ω
5V
4
3
1
2
Figure 4.6. WFM200S Wi-Fi Expansion Kit Power Topology
UG407: WFM200S Wi-Fi
®
Expansion Kit User's Guide
Connectors
silabs.com
| Building a more connected world.
Rev. 1.0 | 15
